Fact of the day

Wednesday, 19 August 2026

Tech & Wearableswell supported · human dataDiscovery of the day

Across 65 studies of wrist-wearable activity trackers, the Fitbit Charge measured steps with under 25% error and the Apple Watch measured heart rate with under 10% error, but energy expenditure was off by more than 30% for every brand tested.

Study design
Systematic review
Journal
J Med Internet Res
Evidence
well supported

What it shows: A trustworthy overview: a sweep of all 65 studies on wrist trackers in the general population. The studies measured accuracy so differently that results could not be combined into one number, so device comparisons are informal rather than head to head.Systematic review · J Med Internet Res

Accuracy and Acceptability of Wrist-Wearable Activity-Tracking Devices: Systematic Review of the Literature. J Med Internet Res 2022Read the study →

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